The FastDay Forum

It's one of those things which pops up in my mind occasionally and I thought I'd put it here, in case anyone had an answer...

Is there a difference in energy expanded to keep the body at an optimum temperature?
Does my body use more energy to keep warm or to keep me cool?
Should I wrap myself up, forcing my body to cool me down, or should I bare it all and encourage my body to keep warm?

Hmmmm...

I think it uses more energy to keep you warm. I think we actually burn alot of calories keeping warm.

By a really strange coincidence , this very question is partly answered in a Kindle book I was skimming through just now.

There's a mention of a study done on Michael Phelps (US swimmer) and the fact that his calorie intake greatly surpasses his activity levels. The conclusion suggests that his body expanded a huge number of calories simply to combat the effect of the cold water he was training in, in order to maintain core temperature.

[carorees]

The answer is cold! Read up about cold hormesis and brown fat! (there's some in this labs section of the forum plus google for lots more!)

Haha!
Now that I know the technical term, I see there's loads of info here!
Thank you

Heat loss is part of calorie requirements, if your body is above ambient temperature that is ! Metabolic rates used to be (and sometimes still are) expressed per unit of body surface area to reflect this.

If you'are at 38 C and the air is at 18 C you will lose 20 units per square metre, if the air is at 8 C that goes up to 30 units and at 28 C it falls to 10 units. The heat loss to water would be much higher (better heat transfer fluid) and shivering is an additional energy burn when that starts (can double resting metabolic rate).

As an example, naked in a slight breeze (2 mph) you lose about 10 Watts per sq.m per C temp difference, so my 2 sq.m loses 2 * 10 * (38 - 18) = 400 Watts

400W is quite a high calorie burn - Bradley Wiggins on the Tour de France - so in practice your skin temperature falls and the temperature difference reduces, reducing the heat loss.

[janeg]

AHA! so the extreme heat here is making me hold on to fat! It all makes sense now!